Automatic assembly apparatus for fastening fasteners, such as screws, bolts, nuts, and the like are known in the art. Generally, prior art automatic assembly machines include a drive head for driving the fastener and a manipulator for positioning the drive head with respect to the workpiece. Additionally, the drive head may be equipped with an automatic feed for providing the fastener to the drive head.
Primarily, these prior art automatic assembly machines represent a trade-off between positioning flexibility and operator comfort. So, where one prior art machine might be extremely flexible, allowing the machine operator to position the drive head as he pleases, repeated flexing force is transmitted to the operator from the drive head as the fastener is torqued down. This repeated flexing force can lead, eventually, to Repetitive Stress Injuries (RSI) such as carpal tunnel syndrome. RSI's occur when a particular portion of the body is repeatedly subjected to the same or similar type of stressful movement or impact, which although normally not injurious, becomes so with repetition.
Prior art efforts to reduce RSI associated with automatic assembly machines focused on reducing carpal tunnel syndrome by foregoing positioning flexibility. By way of example, in U.S. Pat. No. 5,109,736, entitled "Automatic Assembly Machine with Steering/Up-Down Control Handle" to Dixon, incorporated herein by reference, Dixon teaches an automatic screwdriver mounted on a cantilevered support. The support allows the screwdriver to be positioned horizontally on the workpiece by the operator. The screwdriver is activated when the operator forces it downward toward the workpiece. Dixon's automatic assembly machine reduces carpal tunnel from torque because the screwdriver is fixedly mounted to the vertical drive of the support such that it cannot rotate. However, the operator must still apply downward force to Dixon's machine each time a screw is screwed into a workpiece. This repetitive downward force stresses areas of the body such that RSI (even carpal tunnel) can still occur. Further, since Dixon's drive head (screwdriver) is fixedly mounted to the vertical support drive, positioning the driver over the fastener may be difficult, e.g., positioning a drive socket over a nut.